<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    var a = ['a','bb','cc'];
    console.log(a);//数组直接打印出
    document.write(a) //a.toString，先转换成字符串，再在网页上输出，转换时，调用了数组的.toString方法
    document.write(a)
</script>
</body>
</html>